Process to recover benzene from mixed hydrocarbons by extractive distillation

Abstract

Benzene and other aromatics are separated from a stream of mixed hydrocarbons containing both aromatics and non-aromatics by extractive distillation with a solvent system containing dimethyl sulfoxide and optionally a co-solvent, preferably water, followed by distillation stripping of the aromatics from the enriched solvent system, and recycle of the lean solvent system to the extractive distillation step.

What is claimed is: 
     
       1. A method for removing and recovering benzene and/or other aromatic hydrocarbons from a mixed stream containing benzene and/or other aromatic hydrocarbons and mixed non-aromatic hydrocarbons comprising: flowing said mixed stream in countercurrent contact with an extractive distillation solvent system consisting essentially of dimethyl sulfoxide in an extractive distillation column to thereby extractively distill said mixed stream and extractive distillation solvent system to obtain an overhead raffinate stream consisting essentially of said mixed non-aromatic hydrocarbons and a bottoms stream consisting essentially of said benzene and/or other aromatic hydrocarbons, dissolved and/or dispersed in said distillation solvent system;   distilling said bottoms stream in a stripping column to obtain a stripper overhead stream containing said benzene and/or other aromatic hydrocarbons and part of said distillation solvent system, and a stripper bottoms stream consisting essentially of components of said distillation solvent system;   recycling said stripper bottoms stream to said extractive distillation column for extractive distillation with said mixed stream;   separating the stripper overhead stream by condensation and phase separation into an aromatic product stream containing benzene and/or other aromatic hydrocarbons and a solvent stream containing components of said distillation solvent system.   
     
     
       2. A method in accordance with claim 1 and further comprising recycling said solvent stream to said stripping column. 
     
     
       3. A method in accordance with claim 2 and further comprising heat exchanging said solvent stream being recycled to said stripping column with said distillation column bottoms stream. 
     
     
       4. A method in accordance with claim 1 and further comprising fractionating said stripper overhead stream after separation of said solvent stream therefrom to obtain a benzene stream and a stream of aromatics heavier than benzene. 
     
     
       5. A method for removing and recovering benzene and/or other aromatic hydrocarbons from a mixed stream containing benzene and/or other aromatic hydrocarbons and mixed non-aromatic hydrocarbons comprising: flowing said mixed stream in countercurrent contact with an extractive distillation solvent system consisting essentially of dimethyl sulfoxide and water in an extractive distillation column to thereby extractively distill said mixed stream and extractive distillation solvent system to obtain an overhead raffinate stream consisting essentially of said mixed non-aromatic hydrocarbons and a bottoms stream consisting essentially of said benzene and/or other aromatic hydrocarbons, dissolved and/or dispersed in said distillation solvent system;   distilling said bottoms stream in a stripping column to obtain a stripper overhead stream containing said benzene and/or other aromatic hydrocarbons and pan of said distillation solvent system, and a stripper bottoms stream consisting essentially of components of said distillation solvent system;   recycling said stripper bottoms stream to said extractive distillation column for extractive distillation with said mixed stream;   separating the stripper overhead stream by condensation and phase separation into an aromatic product stream containing benzene and/or other aromatic hydrocarbons and a solvent stream containing components of said distillation solvent system.   
     
     
       6. A method in accordance with claim 5 and further comprising recycling said solvent stream to said stripping column. 
     
     
       7. A method in accordance with claim 6 and further comprising heat exchanging said solvent stream being recycled to said stripping column with said distillation column bottoms stream. 
     
     
       8. A method in accordance with claim 5 and further comprising fractionating said stripper overhead stream after separation of said solvent stream therefrom to obtain a benzene stream and a stream of aromatics heavier than benzene. 
     
     
       9. A method for removing and recovering benzene and/or other aromatic hydrocarbons from a mixed stream containing benzene and/or other aromatic hydrocarbons and mixed non-aromatic hydrocarbons comprising: flowing said mixed stream in countercurrent contact with an extractive distillation solvent system consisting essentially of dimethyl sulfoxide and at least one co-solvent selected from the class consisting of dimethyl formamide, methoxybenzene, ethylene glycol, mixed xylenes, morpholine, ethylene glycol butyl ether, all-methyl acetamide, n-ethyl morpholine, water, and mixtures thereof in an extractive distillation column to thereby extractively distill said mixed stream and extractive distillation solvent system to obtain an overhead raffinate stream consisting essentially of said mixed non-aromatic hydrocarbons and a bottoms stream consisting essentially of said benzene and/or other aromatic hydrocarbons, dissolved and/or dispersed in said distillation solvent system;   distilling said bottoms stream in a stripping column to obtain a stripper overhead stream containing said benzene and/or other aromatic hydrocarbons and part of said distillation solvent system, and a stripper bottoms stream consisting essentially of components of said distillation solvent system;   recycling said stripper bottoms stream to said extractive distillation column for extractive distillation with said mixed stream;   separating the stripper overhead stream by condensation and phase separation into an aromatic product stream containing benzene and/or other aromatic hydrocarbons and a solvent stream containing components of said distillation solvent system.   
     
     
       10. A method in accordance with claim 9 and further comprising recycling said solvent stream to said stripping column. 
     
     
       11. A method in accordance with claim 10 and further comprising heat exchanging said solvent stream being recycled to said stripping column with said distillation column bottoms stream. 
     
     
       12. A method in accordance with claim 9 and further comprising fractionating said stripper overhead stream after separation of said solvent stream therefrom to obtain a benzene stream and a stream of aromatics heavier than benzene.